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Tuesday, 14 October 2014

CAPM: An Absurd Model

By professor Pablo Fernandez

ABSTRACT. The CAPM is an absurd model because its assumptions and its predictions/conclusions have no basis in the real world. The use of CAPM is also a source of litigation: many professors, lawyers… get nice fees because many professionals use CAPM instead of common sense to calculate the required return to equity. Users of the CAPM make many illogical errors valuing companies, accepting/rejecting investment projects, evaluating fund performance, pricing goods and services in regulated markets, calculating value creation…

According to the dictionary, a theory is “an idea or set of ideas that is intended to explain facts or events”;and a model is“a set of ideas and numbers that describe the past, present, or future state of something”. With the vast amount of information and research that we have, it is quite clear that the CAPM is neither a theory nor a model because it does not “explain facts or events”,nor does it“describe the past, present, or future state of something”.

It is important to differentiate between a fact (something that truly exists or happens: something that has actual existence; a true piece of information)and an opinion (what someone thinks about a particular thing). The CAPM could be described as anuninformed opinion,and not as asensible opinion.

We all should try to explain a portion of “the world as it is”, not of “the world according to a wrong theory” nor of “the world if men were not men”. Ricardo Yepes, professor of philosophy of my university, wrote: “Learning means being able to keep perceiving reality as it truly is: complex - and not trying to fit every new experience into a closed and pre-conceived notion or overall scheme”.

We may find out an investor’s expected IBM beta and expected market risk premium (MRP) by asking him. However, it is impossible to determine the expected IBM beta and the expected MRP of the market (for the market as a whole), because these two parameters do not exist. Different investors have different cash flow expectations and use different expected (and required) returns to equity (different expected market risk premium and different expected beta). One could only talk of the beta and the market risk premium if all investors had the same expectations. But investors do not have homogeneous expectations.